1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_GC_G1_G1POLICY_HPP
  26 #define SHARE_GC_G1_G1POLICY_HPP
  27 
  28 #include "gc/g1/g1CollectorState.hpp"
  29 #include "gc/g1/g1ConcurrentStartToMixedTimeTracker.hpp"
  30 #include "gc/g1/g1GCPhaseTimes.hpp"
  31 #include "gc/g1/g1HeapRegionAttr.hpp"
  32 #include "gc/g1/g1MMUTracker.hpp"
  33 #include "gc/g1/g1OldGenAllocationTracker.hpp"
  34 #include "gc/g1/g1RemSetTrackingPolicy.hpp"
  35 #include "gc/g1/g1Predictions.hpp"
  36 #include "gc/g1/g1YoungGenSizer.hpp"
  37 #include "gc/shared/gcCause.hpp"
  38 #include "utilities/pair.hpp"
  39 
  40 // A G1Policy makes policy decisions that determine the
  41 // characteristics of the collector.  Examples include:
  42 //   * choice of collection set.
  43 //   * when to collect.
  44 
  45 class HeapRegion;
  46 class G1CollectionSet;
  47 class G1CollectionSetCandidates;
  48 class G1CollectionSetChooser;
  49 class G1IHOPControl;
  50 class G1Analytics;
  51 class G1SurvivorRegions;
  52 class G1YoungGenSizer;
  53 class GCPolicyCounters;
  54 class STWGCTimer;
  55 
  56 class G1Policy: public CHeapObj<mtGC> {
  57  private:
  58 
  59   static G1IHOPControl* create_ihop_control(const G1OldGenAllocationTracker* old_gen_alloc_tracker,
  60                                             const G1Predictions* predictor);
  61   // Update the IHOP control with necessary statistics.
  62   void update_ihop_prediction(double mutator_time_s,
  63                               size_t young_gen_size,
  64                               bool this_gc_was_young_only);
  65   void report_ihop_statistics();
  66 
  67   G1Predictions _predictor;
  68   G1Analytics* _analytics;
  69   G1RemSetTrackingPolicy _remset_tracker;
  70   G1MMUTracker* _mmu_tracker;
  71   G1IHOPControl* _ihop_control;
  72 
  73   GCPolicyCounters* _policy_counters;
  74 
  75   double _full_collection_start_sec;
  76 
  77   uint _young_list_target_length;
  78   uint _young_list_fixed_length;
  79 
  80   // The max number of regions we can extend the eden by while the GC
  81   // locker is active. This should be >= _young_list_target_length;
  82   uint _young_list_max_length;
  83 
  84   // The survivor rate groups below must be initialized after the predictor because they
  85   // indirectly use it through the "this" object passed to their constructor.
  86   G1SurvRateGroup* _eden_surv_rate_group;
  87   G1SurvRateGroup* _survivor_surv_rate_group;
  88 
  89   double _reserve_factor;
  90   // This will be set when the heap is expanded
  91   // for the first time during initialization.
  92   uint   _reserve_regions;
  93 
  94   G1YoungGenSizer* _young_gen_sizer;
  95 
  96   uint _free_regions_at_end_of_collection;
  97 
  98   size_t _rs_length;
  99 
 100   size_t _rs_length_prediction;
 101 
 102   size_t _pending_cards_at_gc_start;
 103 
 104   // Tracking the allocation in the old generation between
 105   // two GCs.
 106   G1OldGenAllocationTracker _old_gen_alloc_tracker;
 107 
 108   G1ConcurrentStartToMixedTimeTracker _concurrent_start_to_mixed;
 109 
 110   bool should_update_surv_rate_group_predictors() {
 111     return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
 112   }
 113 
 114   double logged_cards_processing_time() const;
 115 public:
 116   const G1Predictions& predictor() const { return _predictor; }
 117   const G1Analytics* analytics()   const { return const_cast<const G1Analytics*>(_analytics); }
 118 
 119   G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
 120 
 121   G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
 122 
 123   void set_region_eden(HeapRegion* hr) {
 124     hr->set_eden();
 125     hr->install_surv_rate_group(_eden_surv_rate_group);
 126   }
 127 
 128   void set_region_survivor(HeapRegion* hr) {
 129     assert(hr->is_survivor(), "pre-condition");
 130     hr->install_surv_rate_group(_survivor_surv_rate_group);
 131   }
 132 
 133   void record_rs_length(size_t rs_length) {
 134     _rs_length = rs_length;
 135   }
 136 
 137   double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
 138 
 139 private:
 140   double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
 141 
 142   double predict_region_copy_time_ms(HeapRegion* hr) const;
 143 
 144 public:
 145 
 146   double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
 147   double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
 148   double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
 149 
 150   void cset_regions_freed() {
 151     bool update = should_update_surv_rate_group_predictors();
 152 
 153     _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 154     _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 155   }
 156 
 157   G1MMUTracker* mmu_tracker() {
 158     return _mmu_tracker;
 159   }
 160 
 161   const G1MMUTracker* mmu_tracker() const {
 162     return _mmu_tracker;
 163   }
 164 
 165   double max_pause_time_ms() const {
 166     return _mmu_tracker->max_gc_time() * 1000.0;
 167   }
 168 
 169 private:
 170   G1CollectionSet* _collection_set;
 171   double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
 172   double other_time_ms(double pause_time_ms) const;
 173 
 174   double young_other_time_ms() const;
 175   double non_young_other_time_ms() const;
 176   double constant_other_time_ms(double pause_time_ms) const;
 177 
 178   G1CollectionSetChooser* cset_chooser() const;
 179 
 180   // Stash a pointer to the g1 heap.
 181   G1CollectedHeap* _g1h;
 182 
 183   STWGCTimer*     _phase_times_timer;
 184   // Lazily initialized
 185   mutable G1GCPhaseTimes* _phase_times;
 186 
 187   // This set of variables tracks the collector efficiency, in order to
 188   // determine whether we should initiate a new marking.
 189   double _mark_remark_start_sec;
 190   double _mark_cleanup_start_sec;
 191 
 192   // Updates the internal young list maximum and target lengths. Returns the
 193   // unbounded young list target length. If no rs_length parameter is passed,
 194   // predict the RS length using the prediction model, otherwise use the
 195   // given rs_length as the prediction.
 196   uint update_young_list_max_and_target_length();
 197   uint update_young_list_max_and_target_length(size_t rs_length);
 198 
 199   // Update the young list target length either by setting it to the
 200   // desired fixed value or by calculating it using G1's pause
 201   // prediction model.
 202   // Returns the unbounded young list target length.
 203   uint update_young_list_target_length(size_t rs_length);
 204 
 205   // Calculate and return the minimum desired young list target
 206   // length. This is the minimum desired young list length according
 207   // to the user's inputs.
 208   uint calculate_young_list_desired_min_length(uint base_min_length) const;
 209 
 210   // Calculate and return the maximum desired young list target
 211   // length. This is the maximum desired young list length according
 212   // to the user's inputs.
 213   uint calculate_young_list_desired_max_length() const;
 214 
 215   // Calculate and return the maximum young list target length that
 216   // can fit into the pause time goal. The parameters are: rs_length
 217   // represent the prediction of how large the young RSet lengths will
 218   // be, base_min_length is the already existing number of regions in
 219   // the young list, min_length and max_length are the desired min and
 220   // max young list length according to the user's inputs.
 221   uint calculate_young_list_target_length(size_t rs_length,
 222                                           uint base_min_length,
 223                                           uint desired_min_length,
 224                                           uint desired_max_length) const;
 225 
 226   // Result of the bounded_young_list_target_length() method, containing both the
 227   // bounded as well as the unbounded young list target lengths in this order.
 228   typedef Pair<uint, uint, StackObj> YoungTargetLengths;
 229   YoungTargetLengths young_list_target_lengths(size_t rs_length) const;
 230 
 231   void update_rs_length_prediction();
 232   void update_rs_length_prediction(size_t prediction);
 233 
 234   size_t predict_bytes_to_copy(HeapRegion* hr) const;
 235   double predict_survivor_regions_evac_time() const;
 236 
 237   // Check whether a given young length (young_length) fits into the
 238   // given target pause time and whether the prediction for the amount
 239   // of objects to be copied for the given length will fit into the
 240   // given free space (expressed by base_free_regions).  It is used by
 241   // calculate_young_list_target_length().
 242   bool predict_will_fit(uint young_length, double base_time_ms,
 243                         uint base_free_regions, double target_pause_time_ms) const;
 244 
 245 public:
 246   size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
 247 
 248   // Calculate the minimum number of old regions we'll add to the CSet
 249   // during a mixed GC.
 250   uint calc_min_old_cset_length() const;
 251 
 252   // Calculate the maximum number of old regions we'll add to the CSet
 253   // during a mixed GC.
 254   uint calc_max_old_cset_length() const;
 255 
 256   // Returns the given amount of reclaimable bytes (that represents
 257   // the amount of reclaimable space still to be collected) as a
 258   // percentage of the current heap capacity.
 259   double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
 260 
 261 private:
 262   void clear_collection_set_candidates();
 263   // Sets up marking if proper conditions are met.
 264   void maybe_start_marking();
 265 
 266   // The kind of STW pause.
 267   enum PauseKind {
 268     FullGC,
 269     YoungOnlyGC,
 270     MixedGC,
 271     LastYoungGC,
 272     ConcurrentStartGC,
 273     Cleanup,
 274     Remark
 275   };
 276 
 277   static bool is_young_only_pause(PauseKind kind);
 278   static bool is_mixed_pause(PauseKind kind);
 279   static bool is_last_young_pause(PauseKind kind);
 280   static bool is_concurrent_start_pause(PauseKind kind);
 281   // Calculate PauseKind from internal state.
 282   PauseKind young_gc_pause_kind() const;
 283   // Record the given STW pause with the given start and end times (in s).
 284   void record_pause(PauseKind kind, double start, double end);
 285   // Indicate that we aborted marking before doing any mixed GCs.
 286   void abort_time_to_mixed_tracking();
 287 
 288   // Record and log stats before not-full collection.
 289   void record_concurrent_refinement_stats();
 290 
 291 public:
 292 
 293   G1Policy(STWGCTimer* gc_timer);
 294 
 295   virtual ~G1Policy();
 296 
 297   static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
 298 
 299   G1CollectorState* collector_state() const;
 300 
 301   G1GCPhaseTimes* phase_times() const;
 302 
 303   // Check the current value of the young list RSet length and
 304   // compare it against the last prediction. If the current value is
 305   // higher, recalculate the young list target length prediction.
 306   void revise_young_list_target_length_if_necessary(size_t rs_length);
 307 
 308   // This should be called after the heap is resized.
 309   void record_new_heap_size(uint new_number_of_regions);
 310 
 311   virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 312 
 313   void note_gc_start();
 314 
 315   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 316 
 317   bool about_to_start_mixed_phase() const;
 318 
 319   // Record the start and end of an evacuation pause.
 320   void record_collection_pause_start(double start_time_sec);
 321   virtual void record_collection_pause_end(double pause_time_ms);
 322 
 323   // Record the start and end of a full collection.
 324   void record_full_collection_start();
 325   virtual void record_full_collection_end();
 326 
 327   // Must currently be called while the world is stopped.
 328   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 329 
 330   // Record start and end of remark.
 331   void record_concurrent_mark_remark_start();
 332   void record_concurrent_mark_remark_end();
 333 
 334   // Record start, end, and completion of cleanup.
 335   void record_concurrent_mark_cleanup_start();
 336   void record_concurrent_mark_cleanup_end();
 337 
 338   void print_phases();
 339 
 340   bool next_gc_should_be_mixed(const char* true_action_str,
 341                                const char* false_action_str) const;
 342 
 343   // Calculate and return the number of initial and optional old gen regions from
 344   // the given collection set candidates and the remaining time.
 345   void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
 346                                             double time_remaining_ms,
 347                                             uint& num_initial_regions,
 348                                             uint& num_optional_regions);
 349 
 350   // Calculate the number of optional regions from the given collection set candidates,
 351   // the remaining time and the maximum number of these regions and return the number
 352   // of actually selected regions in num_optional_regions.
 353   void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
 354                                                  uint const max_optional_regions,
 355                                                  double time_remaining_ms,
 356                                                  uint& num_optional_regions);
 357 
 358 private:
 359   // Set the state to start a concurrent marking cycle and clear
 360   // _initiate_conc_mark_if_possible because it has now been
 361   // acted on.
 362   void initiate_conc_mark();
 363 
 364 public:
 365   // This sets the initiate_conc_mark_if_possible() flag to start a
 366   // new cycle, as long as we are not already in one. It's best if it
 367   // is called during a safepoint when the test whether a cycle is in
 368   // progress or not is stable.
 369   bool force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause);
 370 
 371   // This is called at the very beginning of an evacuation pause (it
 372   // has to be the first thing that the pause does). If
 373   // initiate_conc_mark_if_possible() is true, and the concurrent
 374   // marking thread has completed its work during the previous cycle,
 375   // it will set in_concurrent_start_gc() to so that the pause does
 376   // the concurrent start work and start a marking cycle.
 377   void decide_on_conc_mark_initiation();
 378 
 379   size_t young_list_target_length() const { return _young_list_target_length; }
 380 
 381   bool should_allocate_mutator_region() const;
 382 
 383   bool can_expand_young_list() const;
 384 
 385   uint young_list_max_length() const {
 386     return _young_list_max_length;
 387   }
 388 
 389   bool use_adaptive_young_list_length() const;
 390 
 391   void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
 392 
 393 private:
 394   //
 395   // Survivor regions policy.
 396   //
 397 
 398   // Current tenuring threshold, set to 0 if the collector reaches the
 399   // maximum amount of survivors regions.
 400   uint _tenuring_threshold;
 401 
 402   // The limit on the number of regions allocated for survivors.
 403   uint _max_survivor_regions;
 404 
 405   AgeTable _survivors_age_table;
 406 
 407   size_t desired_survivor_size(uint max_regions) const;
 408 
 409   // Fraction used when predicting how many optional regions to include in
 410   // the CSet. This fraction of the available time is used for optional regions,
 411   // the rest is used to add old regions to the normal CSet.
 412   double optional_prediction_fraction() { return 0.2; }
 413 
 414 public:
 415   // Fraction used when evacuating the optional regions. This fraction of the
 416   // remaining time is used to choose what regions to include in the evacuation.
 417   double optional_evacuation_fraction() { return 0.75; }
 418 
 419   uint tenuring_threshold() const { return _tenuring_threshold; }
 420 
 421   uint max_survivor_regions() {
 422     return _max_survivor_regions;
 423   }
 424 
 425   void note_start_adding_survivor_regions() {
 426     _survivor_surv_rate_group->start_adding_regions();
 427   }
 428 
 429   void note_stop_adding_survivor_regions() {
 430     _survivor_surv_rate_group->stop_adding_regions();
 431   }
 432 
 433   void record_age_table(AgeTable* age_table) {
 434     _survivors_age_table.merge(age_table);
 435   }
 436 
 437   void print_age_table();
 438 
 439   void update_max_gc_locker_expansion();
 440 
 441   void update_survivors_policy();
 442 
 443   virtual bool force_upgrade_to_full() {
 444     return false;
 445   }
 446 };
 447 
 448 #endif // SHARE_GC_G1_G1POLICY_HPP